Sire's Polytrope is used to demonstrate the effect of
the earth's rotations on the movement of a rotating body. In this example
the rotating body has been lost. Were it in place inside the gimbals in
the upper right-hand part of the picture, this would easily be recognized
as a form of gyroscope.

A similar apparatus is described in English in the ca.
1900 catalogue of Max Kohl as "The apparatus is provided with bevel-wheels
and serves for demonstrating the following laws: 1. That rotating axes
place themselves parallelly; 2. that the rotation takes place in equal
sense, from [which] is derived: the determination of the meridian and of
the latitude of a place, the invariablness of the rotation-plane, the proof
of the rotation of the earth on its own axis, the conical movement of the
earth: precession of equinoxes, nutation and parallel advancement of the
earth-axis in the space." It is obvious that this is a translation from
the original German. It cost 250 marks, or about $60.

This apparatus is listed at $65 in the 1913 catalogue of
the Société Genovoise (Geneva) for the Construction of Physical
and Mechanical Apparatus. It is on indefinite loan from King's College,
London to the Smithsonian Institution in Washington, D.C.